The Concept of Sensitive Plants and Animals
by Mike Foster
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Most folks are familiar with the phrase "threatened & endangered plants and animals", having heard these words on the evening news or in newspapers and newsletters. We know that these organisms, such as the California Condor, are threatened with extinction and are protected by law under the Endangered Species Act.
Less well understood is the concept of "sensitive plants and animals". The term "sensitive" is used only within the Forest Service to denote species "for which population viability is a concern, as evidenced by:
- A. Significant current or predicted downward trends in population numbers or density.
- B. Significant current or predicted downward trends in habitat capability that would reduce a species existing distribution."
Sensitive species are designated as such by the Regional Forester, and only the Regional Forester can add or delete species from the sensitive species list.
The intent of the sensitive species program is to "avoid actions which may cause a species t become threatened or endangered." This goal is re-stated in the Eldorado National Forest Land and Resource Management Plan: "provide for protection and habitat needs of sensitive plants so that Forest activities will not jeopardize the continued existence of such species."
The Eldorado National Forest currently has 10 sensitive plant species listed for the Forest. One of these, Stebbins' lomatium (Lomatium stebbinsii), has never been observed on the Forest but is suspected to occur here due to the presence of suitable habitat on the Amador Ranger District and the presence of Stebbins' lomatium on the adjoining Stanislaus National Forest. Of the other nine sensitive plant species, each has unique qualities, habitat requirements, and needs for management and protection. For example, yellow-bur navarretia (Navarretia prolifera ssp. lutea) is found only in Eldorado County and is restricted to a narrow east-west band 18 miles long and 8 miles wide centered on the town of Cedar Grove. With such a narrow distribution one might be inclined to think that the Forest Service should avoid impacting this species as much as possible. But, surprisingly, this annual spring wildflower often responds well to disturbance and can be found carpeting short distances of lightly used road. Some populations number it the tens of thousands!
On the other hand, sawtooth-leaf lewisia (Lewisia serrata) (pictured below) is deserving of a "hands off" approach to management. This fleshy perennial is found only within the confines of the American River between the North and Middle Forks. The habitat of this plant consists of steep, new vertical cliffs and bedrock outcrops, often in the "mist zone" of waterfalls. Upstream diversions could reduce stream flows and eliminate the mist that provides favorable habitat for this plant. Thus, the Forest Service conducts surveys for this plant in any area that may be affected by hydro electric developments.
Long-nosed bats play a vital role in maintaining the ecosystems of the Sonoran Desert in the southwestern United States. They are nectivores or nectar eaters and have long tongues adapted to reach deep into flowers to get at the reward inside. Similar to the role hummingbirds play in the day, bats spread pollen from flower to flower during the night. Giant cacti and several species of agave (century plants) are dependent upon bats for pollination. The giant cacti provides food and shelter for many species of wildlife which are indirectly dependent on bats for their survival. Frugivore or fruit eating bats do not need to rely on echolocation to locate food. Flying foxes are considered the farmers of the tropical forests and without them rain forests across the world may perish without the bats pollination and seed dispersing abilities. By consuming fruit that is too ripe to ship to market, flying foxes reduce waste. They may also prevent the destruction of marketable fruit by insects attracted to a buildup of rotting fruit. In West Africa, bats carry 90 to 98% of the seeds of "pioneer plants" that initiate forest regrowth on cleared land and in the Pacific Islands bats are crucial to the survival of over 40% of the tree species. Many of these trees provide economical products including fruit and timber.
The sawtooth leaf lewisia can be identified year round by the very character that inspired its common name, the sawtooth edges of its succulent leaves. Many of the leaves dry up and shrivel as the summer progresses, especially in the fifth year of a drought, but most plants retain a few green leaves in the center of their rosettes. Look for this plant along the south side of east west trending streams. Especially along the inner gorges of Silver Creek, Wallace Creek, and the Rubicon.
Information on the Eldorado National Forest's showiest sensitive plant species, Pleasant Valley Tulip (Calochortus Clavatus var. avius) will be presented in the next part of this series
Continue to Part 2 >
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